1. Field of the Invention
This invention relates to an internal combustion engine analyzing system and, more particularly, to an electronic testing system for analyzing certain engine operating characteristics.
2. Description of the Prior Art
A number of electronic analyzers have been proposed heretofore to indicate various performance characteristics of internal combustion engines, and particularly the functioning of the ignition system. Also, it has been previously proposed to electronically determine the relative contribution of each cylinder to overall performance of the engine by rendering any desired cylinder inoperative, while the engine is running, without affecting the operation of the other cylinders. These devices of the prior art have frequently employed cathode ray oscilloscopes to provide a visual display of test data. Additionally, timing advance measuring apparatus have been proposed heretofore which will produce an indication of the degree of advance ahead of the top dead center position of the piston in the cylinder. Representative devices of the aforementioned types are disclosed in respective ones of U.S. Pat. Nos. 2,355,363; Re 26,163; 3,404,333 and 3,368,143.
These prior art instruments have not been widely employed in diagnostic and service shops due to certain complexities in their use, difficulties encountered in their calibration, and for other reasons which will be discussed hereinafter. For example, in an engine analyzer of the type which selectively represses ignition in a given cylinder, it has been the practice heretofore to anticipate cylinder fire, in order to short out the desired cylinder, by timing from the instance of the previous cylinder fire. This technique imposes a practical restriction on the engine r.p.m. Therefore, dynamic tests over a wide range of operating conditions cannot be made.
If the anticipation of cylinder fire can be related to rotational degrees of the engine, instead of time since the previous cylinder fire, then the system may be made to operate independently of engine r.p.m. Such is the case in the present invention. Other improvements over engine performance analyzers of the prior art will be described in a subsequent part of this specification.